We were successful in ascertaining the presence of the compounds of the following structural formulas with ansamycin skeleton having anti-tumor activities in the fermentation product of a new strain Streptomyces rishiensis T-23 (deposited at "Fermentation Research Institute, Agency of Industrial Science & Technology, MITI (Japan)" under the deposit No. FERM P-6141), ##STR1## The above-mentioned compounds were then named in that order compound T-23-I, compound T-23-II, compound T-23-VIII and compound T-23-IX, respectively. The compounds T-23-I and -II were filed on Nov. 24, 1982 as U.S. Ser. No. 444,474 and issued on June 4, 1985 as U.S. Pat. No. 4,521,339, and the processes for the preparation thereof was filed on Jan. 29, 1985 as U.S. Ser. No. 696,040 which is a division of U.S. Ser. No. 444,474. Further, the compounds T-23-VIII and -IX were filed on Sept. 6, 1985 as U.S. Ser. No. 773,445.
According to our previous findings, the compounds T-23-I, -II, -VIII and -IX are prepared in the following manner.
More particularly, Streptomyces rishiensis T-23 strain mentioned above is cultured according to the conventional method for the culture of Actinomyces strain. The culture broth obtained in then divided into mycelia and a supernatant. An active fraction is extracted with acetone-water from the mycelia. The extract containing the active fraction is passed through a nonionic exchange resin to effect absorption of the active fraction thereon, followed by extraction with a solvent such as acetone or a lower alcohol. Separately, the active fraction is also extracted with an organic solvent directly from the supernatant. The two extracts are combined, and the organic solvent is removed from the mixture to give an aqueous phase which is then extracted with a water-immiscible solvent such as chloroform or ethyl acetate and then concentrated. Thereafter, the concentrate is charged with an aliphatic hydrocarbon solvent to precipitate the active fraction which is then adsorbed onto a silica gel column. After washing with benzene, the column is eluted with benzene-acetone (4:1) to obtain a T-23-I containing solution. The elution of the silica gel column is further continued with the same solvent to give a solution containing T-23-VIII. This column is further eluted with benzene-acetone (7:3 ) to obtain a T-23-II containing solution. After obtaining the T-23-II containing solution, the elution of the column with the same solvent is further continued, whereupon a T-23-IX containing solution is obtained.